#include <bits/stdc++.h>

using namespace std;

int ask(int x){
    cout << "? " << x << endl;
    cout.flush();

    cin >> x;
    return x;
}

int main()
{
    int n;
    cin >> n;

    int last = 0;
    int x = ask(1);

    if(x == last){
        cout << "! " << 1 << "\n";
        return 0;
    }

    last = x;

    int l = 2 , r = n;
    while(l < r){
        int mid = (l + r) >> 1;
        x = ask(mid);
        if(x == last){
            cout << "! " << mid << endl;
            return 0;
        }
        if(x > last) {
            l = mid + 1;
            last = x;
        }else {
            r = mid - 1;
            last = x;
        }
    }

    cout << "! " << r << endl;
    return 0;
}